A dual engine-triggered DNA walker based on luminous perylene-TiO2 nanospheres for efficient electrochemiluminescence bioassay

Despite the intrinsic programmability and flexible biological functions of DNA walkers, it remains challenging for traditional DNA walkers to precisely control mechanical running paths in nanoscale spaces. In this work, an elegant dual engine-triggered DNA walker was elaborated based on precise orientation protocol, applying the DNA cube as the scaffold for anchoring the dual swing arms as engines and tracks as signal switches. The order arrangement and dual engines enhanced the operating efficiency and controllability of the DNA walker markedly. Moreover, the electrochemiluminescence (ECL) molecule perylene doped-titanium dioxide (Pe-TiO2) organic–inorganic nanospheres with low cost and high reproducibility were synthesized as the ECL emitters by one-step sol–gel method. It was worth noting that TiO2 gel not only restricted the stacking mode of Pe molecules in vibration and rotation, but also enhanced the interfacial charge transfer ability in organic–inorganic hybrid mode, resulting in the improvement of ECL efficiency and structural stability. Based on the luminous Pe-TiO2 nanospheres, a ternary ECL system was proposed with S2O82− as coreactant, and silver nanoparticles (Ag NPs) as coreaction accelerator. Ultimately, by combing the dual engine-triggered DNA walker with the ternary ECL system, an efficient ECL bioassay platform was developed for microRNA let 7a (let-7a) detection with a wide linear range from 10 fmol/L to 100 nmol/L and a low detection limit of 7.0 fmol/L. Hence, this work offered a universal strategy to predesign walking paths and improve loading capacity in virtue of DNA nanostructures, as well as to expand the biology research of planar organic luminophores in an organic–inorganic hybrid manner.